JPS62150620A - Covering assembly of vacuum breaker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to vacuum circuit breakers, and more particularly to the assembly of vacuum circuit breaker jacket components.

Background of the invention The vacuum circuit breaker includes an evacuated envelope that is roughly cylindrical in shape.

The members at both ends of the jacket each support a movable contact rod and a fixed contact rod that support the contacts. The contacts are opened and closed by moving the movable contact rod. The outer cover includes a metallic member and an insulating member for electrically insulating between the movable contact rod and the fixed contact rod. These members must be secured to form a mechanically strong and heat resistant envelope structure to maintain an airtight seal that maintains an internal vacuum. Typically, the external wave components are joined in butt contact, with the end face of one member being secured or brazed to the corresponding end face of another member. Seams between components must be properly sealed or brazed to prevent leakage. Even a small leak can cause equipment failure. It is therefore desirable to minimize the number of jacket components to be joined, and therefore the number of jacket seams to be brazed, to reduce the risk of leakage and failure.

Because the jacket components are bonded or brazed at high temperatures, generally in the range of 800 to 1050 degrees Celsius, they are prone to thermal expansion during their assembly. When dissimilar materials with different thermal expansion coefficients, i.e., an insulating member and a metal member, are bonded together, stress is likely to occur due to the difference in thermal expansion and subsequent difference in thermal contraction. Invite destruction. Even a very small break in the seam can cause the seal to fail and thus render the circuit breaker inoperable. For this reason, it is desirable that all the materials of the jacket have the same coefficient of thermal expansion to eliminate differences in expansion and contraction. However, the envelope components must be selected to meet various characteristics and performance requirements. For this reason, it is difficult to obtain satisfactory insulating members and metal parts having substantially the same coefficient of thermal expansion.

Therefore, other solutions are needed to prevent stresses that cause breakage. Such a solution should not unduly complicate the method of assembling the circuit breaker, nor should it require extra parts in the jacket structure.

The number of jacket components, and therefore the number of seams between the parts, must be reduced to reduce the possibility of leakage.

OBJECTS OF THE INVENTION It is an object of the present invention to have adequate strength and stiffness to withstand the forces of atmospheric pressure and the mechanical forces applied during actuation of the contacts, yet designed to minimize stresses that may cause breakage. An object of the present invention is to provide a circuit breaker having an outer jacket.

Another object of the invention is to provide a circuit breaker jacket in which a metal component and an insulating component are butt joined to create a relatively low stress joint.

Another object of the present invention is to provide a circuit breaker jacket in which a central cylindrical insulating member is brazed to each end with a unitary metal end member in a substantially stress-free manner.

SUMMARY OF THE INVENTION In accordance with the present invention, first and second metal end members are joined to opposite ends of a cylindrical casing of insulating material. Movable and fixed contact rods each extend through and are supported by the end member. At least one of the end members is an integrally formed unitary structure having a bottom portion and a cylindrical side wall, the bottom portion supporting one of the contact rods, and an end face of the cylindrical side wall being secured to an end face of the casing. , for example brazed. This unitary structure must have sufficient rigidity to withstand atmospheric pressure forces and mechanical actuation forces.

The wall thickness of the cylindrical portion extending from the end face towards the bottom portion forming part of the cylindrical side wall is substantially reduced with respect to the wall thickness of the other portion of the end member to form a cylindrical shape. To be able to absorb the difference in thermal deformation between the side wall and the insulating casing. In a preferred embodiment, both end members are configured as described above.

DESCRIPTION OF THE EMBODIMENTS To better understand the invention. The invention will now be described in detail with reference to the accompanying drawings.

The present invention is applicable to the general type of vacuum circuit breaker shown in FIG. The illustrated vacuum circuit breaker comprises a highly evacuated jacket 11 having a tubular or cylindrical casing 12 of electrically insulating material and two metal end pieces 13 and 14.

Within this jacket 11 there are two relatively movable contacts 15.
and 16 are arranged.

The contact 15 is a fixed contact and is supported by a fixed contact rod 17 that extends through the upper end member 13 in a sealed manner. The contact 16 is a movable contact and is connected to the lower end member 14.
The contact rod 18 is supported by a movable contact rod 18 which freely passes through a central opening 19 of the contact rod 18 .

A retractable metal bellows 22 forms a seal around the movable contact rod 18. The bellows 22 has its upper end 23
is joined to the movable contact rod 18 and its lower end 24 is joined to a peripheral wall defining a central opening 19 in the lower end member 14 .

The illustrated state of the circuit breaker is in the open position, ie, contacts 15 and 16 are spaced apart from each other.

Opening of the contacts is accomplished by driving the movable contact rod 18 upward to bring the contacts into contact.

Lowering the movable contact rod 18 to the position shown opens the contact or breaks the circuit.

Opening or separating the contacts creates an arc between the contacts, which typically lasts until the current drops to zero. The interruption is complete when the current reaches zero. The metal vapor produced by the arc adheres to surrounding surfaces.

A bellows shield 29 is provided to protect bellows 22 from metal vapors.

Also, since it is necessary to prevent metal vapor from adhering to the insulating casing 12, a tubular metal main shield 26 is provided. The main shield 26 is fixed concentrically to the inner circumference of the insulating casing 12. To achieve this fixation, for example, metal clips 27 are fixed by spot welding at equal intervals around the outer circumference of the main shield 26 at the longitudinal center thereof. The clip 27 engages a projection 28 that projects inwardly from the casing 12.

The insulating casing 12 is further protected from metal vapor deposition by end shields 32 and 33. A metal upper end shield 32 and a metal lower end shield 33 are secured to the upper end member 13 and the lower end member 14, respectively, to connect the insulating casing 12 and the main shield 2.
It extends concentrically between 6 and 6. Therefore, metal vapors escaping from the ends of main shield 26 will be removed from end shields 32 and 33.
is prevented from reaching the insulating casing 12.

No. 796,148, filed November 8, 1985 by the present applicant, discloses that
3 is fixed to the outer cover of the vacuum circuit breaker.

The jacket of the circuit breaker consists of an insulating casing 12 and end members 13 and 14 that seal the ends of this casing. In one embodiment, the cylindrical insulating casing 12 is made of a dense impermeable material coated with a glaze.
Made of low-loss, vacuum-tight, high-alumina ceramic. A thin metal coating 54 (FIGS. 2 and 3) is provided on both ends 53 of the casing 12 to facilitate brazing. The coating may consist of a refractory or sintered metal coating approximately 1 mil thick and an outer, thinner electroplated and sintered nickel coating. Ceramics, glazes and metal coatings must withstand temperatures up to about 1000° C. without degrading.

In a preferred embodiment, casing 12 has a height of approximately 4 inches, an inner diameter of approximately 4.6 inches, and a wall thickness of approximately 0.5 inches. It is 25 inches.

End members 13 and 14 are generally bell-shaped or cup-shaped unitary structures consisting of a bottom portion 51 and an integral continuous cylindrical side wall 38. The bottom part 51 is provided with a central hole 19 through which the contact rod passes, and a curved part 52 of the bottom part leads to the side wall 38 . In the preferred embodiment described above, the end member is approximately 2 inches tall and the cylindrical sidewall has an inside diameter of approximately 4.8 inches. The end members are formed from sheet metal material, such as #304 steel sheet. In the preferred embodiment described above, the thickness of the sheet material is approximately 0.0
It is 6 inches. The thickness of the sheet material is selected so that the end members have sufficient strength to support the contact rod and contact assembly and to withstand atmospheric pressure. The diameters of the cylindrical side wall 38 and the insulating casing 12 are such that the end surface 55 of the side wall 38 butts into the end surface 53 of the casing 12, ie, the metal coating 54.

The wall thickness of the casing 12 is substantially greater than the wall thickness of the end members. Preferably, the interface between the casing and each end member is located approximately midway between the inner and outer wall surfaces of the insulating casing 12.

The steel sheet of the seed lamp i is non-magnetic.

Magnetic flux is generated during operation of a vacuum circuit breaker. This magnetic flux passes through the end member. If the end member is made of magnetizable material, eddy currents will be generated which will cause an undesirable temperature increase in the end member.

The insulating casing 12 and the end pieces 13 and 14 have different coefficients of thermal expansion. The coefficient of linear expansion of the casing 12 is between 7°5 and 9.0×10' in the temperature range of interest.
inch/inch/°C.

The coefficient of linear expansion of #304 steel sheet is greater, approximately 17.3 x 10' inches/inch/°C.

When assembling the circuit breaker jacket, i.e. when brazing the end faces of the end pieces 13 and 14 to the end face of the casing 12,
The jacket component is heated to a temperature of approximately 1000°C. This results in significant differential expansion. Specifically, as the casing and end member are heated in abutting contact, the portion of the cylindrical sidewall 38 adjacent the interface expands radially. Therefore, the end surface 55 of the side wall 38 is
2, ie, along the metal coating 54, toward the outer wall surface of the casing. When the jacket assembly is cooled, the molten braze at the interface between the end member and the casing solidifies as the alloy cools. In this way, the end face 55 of the end member is brazed to the end face of the casing 12 and the metal coating.

During cooling, differential shrinkage occurs between the casing 12 and the end member sidewalls 38. However, the respective end faces 53 and 5
The interface between them is then brazed and fixed. Therefore, the end face 55 of the end member cannot move radially inwardly along the end face of the casing 12. As a result, the end face 5
The portion of the side wall adjacent 5 deforms inwardly towards the central axis of the circuit breaker.

This creates large stresses at the interface between the end member and the casing. This residual stress can cause the braze seal between the end member and the casing to rupture. Even a slight rupture may damage the vacuum pair and cause the vacuum circuit breaker to become inoperable.

According to the present invention, the wall thickness of the cylindrical sidewall 38 is sufficiently thin to minimize stress at the interface. The reduced wall thickness allows the walls to flex sufficiently to minimize the stresses that occur during heating and cooling during external wave assembly. However, the wall thickness of the entire end member cannot be made sufficiently thin. This is because if the overall thickness is made thinner, the end members become excessively weak.

Furthermore, it is undesirable to provide a separate part, for example a cylinder with a thin wall thickness, between the end piece and the casing. This would require at least one extra circular seam at each end of the jacket assembly. Providing such extra seams requires additional cost and effort, and is always susceptible to seal failure and vacuum seal failure.

For this reason, in the present invention, the wall thickness of the cylindrical portion 56 extending from the end surface 55 of the side wall 38 of the end member toward the bottom portion 51 is reduced. In the preferred embodiment described above, this cylindrical portion 56 of the sidewall has a wall thickness of less than 0.05 inches, such as 0.05 inches.
Thin the outside of the sidewalls to 0.02 inches. The wall thickness of this cylindrical portion 56 may be, for example, approximately half or less (less than 60%) of the wall thickness of the remainder of the end member.

In the preferred embodiment described above, the width or length of cylindrical portion 56 from end face 55 is between 0.1 and 0.5 inches, such as about 0.3 inches. Therefore, the thin walled cylindrical portion 56 occupies only a small portion of the overall height of the end member (eg, 2 inches). This cylindrical portion 56 is sufficiently thin and long enough to provide sufficient deflection to minimize residual stress at the seam between the end member and the casing. Conversely, it has been determined that the reduced wall thickness of cylindrical portion 56 is short enough and thick enough not to compromise the structural integrity of the circuit breaker jacket structure.

It is preferable to braze the end members to the insulating casing 12 using an alloy. For this purpose, a ring of brazing filler metal 5
7 can be interposed between the end member and the metal end face of the insulating casing. Preferably, the brazing filler metal ring 57 is temporarily attached, for example, by spot welding to the end surface 55 of the end member, before brazing. The end piece with the filler metal ring can then be placed adjacent to the casing 12 for brazing. The braze master alloy used in the preferred embodiment is an alloy having a melting point of 925°C and a solidification temperature of 880°C.

The vacuum circuit breaker can be assembled as follows. The end members are formed from sheet metal material in such a way that they do not generate stresses that may cause breakage. The sheet abrasions, such as #304 steel, are first annealed or softened. The end piece is then die formed into a cup or bell shape consisting of a bottom portion 51 and a cylindrical side wall 38. Next, the side wall 38
A flat end surface 55 is precisely formed by cutting. after that,
Portion 56 is formed by cutting or reducing the thickness of a portion of sidewall 38 as described above. The end pieces are annealed again before these steps are completed so that the resulting end pieces are stress-free.

After the end pieces are fabricated, the internal components are assembled using conventional techniques. For example, the components on the stationary end side and the components on the movable end side, that is, the working end side, can be assembled separately using rings or shims made of suitable brazing material. If desired, an end shield can be inserted into the cup-shaped end member, as described in the above-cited US patent application Ser. No. 796,148. Next, the fixed end assembly and the movable end assembly are brazed separately. Insert the main shield 26 into the casing 12, such as a tab or clip 27.
to secure it to the casing. Finally, the fixed end assembly and the movable end (operating end) assembly are fixed to the insulating casing 12 as described above, the circuit breaker is brazed, and the air is evacuated.

Although specific embodiments of the invention have been described, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. Therefore, all such variations and modifications are considered to fall within the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a vacuum circuit breaker using the present invention, FIG. 2 is an exploded perspective view showing an end member, an end shield, and a brazing material ring used for fixing these parts, FIG. 3 is an end member, FIG. 2 is an exploded cross-sectional view of a portion of the insulating casing and braze ring. (Explanation of main symbols) 11...Outer cover, 12...Casing, 13', 14
...End member, 15.16...Contact, 17...Fixed contact rod, 18...Movable contact rod, 26...Main shield, 27...Clip, 28...Protrusion, 32
．． 33... End shield, 51... Bottom portion, 53.
56... End face, 54... Metal wave film, 56... Cylindrical portion with reduced wall thickness.

Claims (1)

Claims: 1. (a) a cylindrical casing of insulating material and first and second end members of metal hermetically joined to opposite ends of the casing; (b) said first and second end members, respectively; a movable contact rod and a fixed contact rod extending through and supported by the second end member; (c) at least one of the end members having an integrally formed bottom portion and a cylindrical sidewall; (d) said bottom portion supports one of said contact rods; (e) said cylindrical side wall has an end surface secured to a corresponding end of said cylindrical casing; f) A wall thickness of a cylindrical portion of the cylindrical side wall extending from the end surface toward the bottom portion,
The wall thickness of the cylindrical side wall is substantially reduced relative to the wall thickness of the other portion of the cylindrical side wall and the bottom portion, and the cylindrical portion with the reduced wall thickness reduces the thermal deformation difference between the cylindrical side wall and the casing. Vacuum circuit breaker characterized by absorption. 2. The vacuum circuit breaker according to claim 1, wherein said one end member is approximately cup-shaped. 3. The vacuum circuit breaker according to claim 1 or 2, wherein the wall thickness of the cylindrical portion is less than 60% of the wall thickness of the other portion of the cylindrical side wall and the bottom portion. 4. The vacuum circuit breaker of claim 3, wherein the wall thickness of the cylindrical portion is less than 0.05 inch. 5. The vacuum circuit breaker according to claim 3, wherein the width of the cylindrical portion is in the range of 0.1 to 0.5 inches. 6. Both ends of the casing are provided with a metallization layer, and the end surface of the cylindrical side wall is substantially flat and is brazed to the metallization layer provided on a corresponding end of the casing. A vacuum circuit breaker according to claim 1 or 2. 7. The at least one end member is formed from a sheet metal material of substantially uniform thickness, and the wall thickness of the cylindrical portion is reduced relative to this uniform wall thickness. Vacuum circuit breaker as described in section. 8. The vacuum circuit breaker according to claim 7, wherein the wall thickness of the cylindrical portion is reduced at its outer periphery. 9. (a) a cylindrical casing of insulating material and first and second end members of metal sealingly joined to opposite ends of the casing; (b) each of said first and second end members; (c) the bottom portions of said first and second end members respectively extend the length of the circuit breaker to the movable contact rod and the fixed contact rod; (d) each of the cylindrical side walls of the first and second end members has an end surface fixed to one end corresponding to the casing; a cylindrical portion extending from the end surface toward the bottom portion has a wall thickness that is substantially reduced relative to the wall thickness of the other portion of the cylindrical side wall and the bottom portion; A vacuum circuit breaker characterized in that thermal deformation between the cylindrical side wall and the casing is absorbed by a thin cylindrical portion of the casing. 10. The vacuum circuit breaker of claim 9, wherein said end member is formed from sheet metal material of substantially uniform wall thickness except for a reduced wall thickness of said cylindrical portion. 11. The vacuum circuit breaker of claim 10, wherein each of said end members is generally cup-shaped. 12. The vacuum circuit breaker according to claim 9 or 10, wherein a main shield is arranged concentrically around the movable contact rod and the fixed contact rod, and the main shield is fixed to the casing. . 13. The vacuum circuit breaker of claim 12, wherein the casing has at least one internal protrusion, and the main shield has a locking tab, the tab engaging the internal protrusion. . 14. The vacuum circuit breaker of claim 12, wherein generally conical first and second end shields are secured to the cylindrical side walls of the first and second end members, respectively. 15. A method for manufacturing a vacuum circuit breaker comprising a cylindrical casing of insulating material and an end member brazed to the casing and supporting a contact rod, comprising: (a) a sheet of predetermined thickness; (b) forming from the sheet material a generally cup-shaped end member having a perforated bottom portion and a cylindrical sidewall integral with the bottom portion and terminating in an end surface; and (c) as described above. (d) reducing the wall thickness of a portion of the cylindrical side wall extending from the end surface toward the bottom portion; (d) annealing the cup-shaped end member to remove internal stress; (e) contact point; (f) providing a metallized coating on at least one of the ends of the cylindrical insulating casing; (g) attaching the end surface of the end member to the cylindrical insulating casing; Vacuum interruption, including brazing to the metallized coating of the casing, thereby deforming the thinned portion of the cylindrical side wall to relieve residual stress at the interface between the end member and the insulating casing. How to make the utensils.